the sum of a geometric sequence with a common ratio or r and a fist term of a1 and summing to term n is [tex] \frac{a_1(1-r^n)}{1-r}[/tex] common ratio is 3=r first term is 4 13 terms [tex] \frac{4(1-3^13)}{1-3}[/tex]= [tex] \frac{4(1-3^13)}{-2}[/tex]= 3188644
